There are currently three books in the Servant to Lust series

Vehicle of Vengeance starts the 
series as Karla  realizes her
vampiric lover betrays her.  As
the betrayal leaves her at death's
door, the elementer Alandra
appears to save her.  Karla
realizes she is now the Servant to
Lust as she fights the renegade
vampires to protect humanity and
her mistress. 
Order at
http://www.amazon.com/Vehicle-Vengeance-Fae-Gatekeeper-Dreams/dp/1435717155/ref=sr_1_1?ie=UTF8&s=books&qid=1304731678&sr=8-1

Slave to a Duty is when Karla
realizes the importance of her
work especially as new
developments happen to her
mistress Alandra.  The elementer
of Lust has a few surprises for
her servant and Karla is faced
with new enemies and a new
friend.

Order by clicking the link here

Delusions of Desire is the most
recent book in the series.  Here
readers find Karla face to face
with new enemies who easily
hide in the dark.  She is also
face to face with more betrayal
but she rises to fight all evil
again.  The book features
black and white artwork at the
start of each chapter.  

Order by clicking the link here.